The present invention relates to the behavior of plate or sheet structures in changing conditions, for example, in a fluid flow, and control of such behavior. Perhaps the most developed body of related art is the study of aerodynamic structures such as aircraft wings, for which detailed models of lifts, loading, flutter control, gust alleviation and the like have been developed for a variety of wing shapes and articulated control systems under a commonly experienced range of conditions. Aileron-controlled wings, however are relatively heavy and unresponsive structures with rather low-bandwidth control systems.
Some current and many future space vehicle and aircraft performance criteria demand light weight flexible structures, such as solar arrays, signal collectors, antennae, mirrors, and lifting surfaces, formed of generally plate-like structures. Structural integrity and mission requirements of these plate-like components of aerospace vehicles also demand low vibration and load levels. Due to these conflicting specifications there exists a need for high-authority, high-bandwidth control systems to be incorporated into and implemented on such plate-like structures.
In the past, it has been suggested that certain structural elements, such as plates or trusses, may incorporate piezoelectric elements actuated to alter the stiffness and suppress an unwanted resonance.
More recently, applicants and others have made various measurements or models relating the performance or weight penalties of distributed actuators for achieving desirable structural properties, for example, induced bending or twisting, of a wing. Thus, at this point it is well recognized that the inclusion of piezoelectric elements in a wing surface is feasible, and the effects of including such elements on basic mechanical properties such as length, stiffness or the like can be quantified. However, there does not appear to have been constructed a control system for performing complete control of a plate structure in a real environment.
It would be desirable to have an effective compensator for controlling an adaptive surface structure such as a lifting surface.